Here’s a related objection that may be easier to see as a valid objection than counterfactual mugging: Suppose you’re about to be copied, then one of the copies will be given a choice, “A) 1 unit of pleasure to me, or B) 2 units of pleasure to the other copy.” An egoist (with perception-determined utility function) before being copied would prefer that their future self/copy choose B, but if that future self/copy is an egoist (with perception-determined utility function) it would choose A instead. So before being copied, the egoist would want to self-modify to become some other kind of agent.
Here’s a related objection that may be easier to see as a valid objection than counterfactual mugging: Suppose you’re about to be copied, then one of the copies will be given a choice, “A) 1 unit of pleasure to me, or B) 2 units of pleasure to the other copy.” An egoist (with perception-determined utility function) before being copied would prefer that their future self/copy choose B, but if that future self/copy is an egoist (with perception-determined utility function) it would choose A instead. So before being copied, the egoist would want to self-modify to become some other kind of agent.